blackholes dont necessarily suck up everything, but it pulls things with an incredibly strong gravitational pull, not even light can escape its pull, thats why its dangerous

if we were to create one, and if it was to get out of control. Would hl2's grav gun be helpful?>. I'm just interested

heh, noe.
first of all, its fiction.
secondly, its not stong enough.
thirdly, you wouldn't be able to see it before you got pwned.
fourth(ly?), you wouldn't be strong enough to pull the trigger.
fifth and lastly, it would break way before you knew it.